Shelter is a basic need, mid human ingenuity has arrived at numerous and sophisticated methods and materials to meet this need. Among the many methods include those employing precast concrete units that are assembled to create a building or other structure. These methods encompass construction systems incorporating a wide range of precast unit designs that vary from the simple to the very complex. The most elementary precast unit designs are those used in basic, concrete masonry. While concrete masonry units (CMU's) may be designed for a variety of applications, they can result in structures that are structurally inferior to those created with larger, reinforced concrete units. Smaller CMU's can crack and chip as well. Construction with small CMU's also requires a specialized labor force. As a result, building methods utilizing CMU's can create high labor costs, and it can be difficult to find a qualified work crew.
More sophisticated construction systems use concrete columns, beams, and foundation members to create a superstructure. A beam and column joining assembly is set forth in U.S. Pat. No. 4,583,336, issued to Shelangoskie, et al. on Apr. 22, 1986. U.S. Pat. No. 5,103,613 issued to Satoru Kinoshita on Apr. 14, 1992 teaches foundation members interconnected by a binding member having mortises therein for receiving tenons on the bottom of a column. U.S. Pat. No. 4,124,963 issued to Tadayasu Higuchi on Nov. 14, 1978 sets forth a precast unit for providing a footing for a building. While the above patents describe a superstructure they provide no teachings on the construction of walls or the like. In addition, the precast units of the inventions provide little flexibility for increasing structural integrity of the larger structure.
Two U.S. Patents present precast units in which wall members are also employed. U.S. Pat. No. 4,328,651 issued to Manuel Gutierrez on May 11, 1982 shows a system having a number of precast units including footing boxes, grade beams, roof beams and a wall panel. The Gutierrez system sets forth an intricate system of interconnecting parts. The intricacies of the design limit the flexibility of the system, however. The beams and wall panels described therein would have to be formed to custom lengths and heights in order to meet the needs of differing structures. In addition, the wall panels lack flexibility for increasing structural strength. The second patent is U.S. Pat. No. 5,081,805 issued to M Omar A. Jazzar on Jan. 21, 1992. This patent teaches precast ) units of half-story height that include steel reinforcements. Tile Jazzar invention requires substantial lifting equipment, however, and is also limited in versatility. Furthermore, building designs departing from preformed dimensions require a second, expensive mold, or considerable custom work to arrive at the desired shape.
Authors David A. Sheppard and William R. Phillips illustrate unitary load-bearing or non-load-bearing precast panels in their book Plant-Cast Precast & Prestressed Concrete--A Design Guide, Third Edition, McGraw-Hill Inc., 1989, (see pages 311-13). The same book also illustrates the use of very large, precast, concrete "voided" bearing walls at page 340. The large bearing walls and precast panels, like those in the Gutierrez patent, must be custom formed and require large custom molds, a large site slab, and very large lifting equipment. In addition, the immense size of the walls makes them impractical for smaller construction projects.
Illustrated in a commercial brochure of American ConForm Industries, Inc. (1993), is a modular construction system that employs stackable polystyrene units. Concrete is poured within the stacked units to create walls for different applications. The design of the units allows for the placement of reinforcing steel, but the units themselves are non-structural. Such a system suffers from a number of problems, including those inherent in having to pour large quantities of concrete, such as delays due to inclement weather conditions and the creation of clutter and debris at the work site. Moreover, strict engineering tolerances are difficult to obtain without skilled workers.
To the inventors' knowledge, no building system employing preformed building units has been developed that provides versatility in design, can accommodate a variety of reinforcement designs for great structural strength, requires relatively small lifting equipment, allows for the rapid construction of buildings, and that does not suffer from the limitations of poured concrete systems.